Locations within books have traditionally been indicated by page numbers. However, the concept of a “page” is not as meaningful in the context of electronic books, in which page divisions may be calculated dynamically as a function of page and font size. Different book reader devices have different display sizes, and even within a particular device a user may change viewing options to result in different effective page sizes.
Because of this, electronic books are often submitted for publication without any indications of page numbering. Within electronic books such as these, locations are often referenced in terms of an index that relates to a smaller unit of measure, such as by a byte/character offset or a word offset. For example, a particular word might be specified in terms of its starting and ending byte or character indexes, relative to the beginning of the electronic book. However, this can result in confusion when trying to cite from particular locations within electronic books, and when trying to navigate to particular locations within electronic books.